We popose to improve oral health and reduce costs of rural school-based caries prevention programs using comparative effectiveness and quality improvement methods. We will test the hypothesis that comprehensive caries prevention is more effective than incremental prevention. Significance. Caries is a preventable bacterial infection, yet 25% of U.S. school children have untreated decay - five-times more than asthma. The prevalence doubles for rural, racial and ethnic minority populations. Effective preventive interventions, recommended by the Centers for Disease Control and Prevention, are available. However, they are often underused and rarely evaluated for clinical effectiveness. Approach. Using a cohort design, we will longitudinally evaluate and compare comprehensive and incremental caries prevention programs in rural elementary schools. Using this comparative data we will generate, implement and test oral health improvement models for clinical and cost-effectiveness. Specific Aims. 1). Develop a manual of procedures, standardize and calibrate caries diagnosis using NHANES diagnostic criteria, implement electronic readable forms for recording, submission, and analysis. 2). Comparatively evaluate clinical and cost-effectiveness, model optimal care and timing, and mentor site improvement programs. 3). Create a database to generate alternate models for caries prevention and open this database for clinical and research use. Impact and Innovation. To our knowledge, this will be the first comparative effectiveness study (including economic assessment) with the breadth and depth to identify and disseminate effective prevention protocols. An added benefit will be the creation of a rich database for modeling prevention in other locations. Environment and Investigators. Forsyth is a century old. Harvard affiliated, oral health research institute. We will marry this talent with the Boston University Data Coordinating Center and school-based caries prevention programs serving ~10,000 children in 67 school, in 10 rural counties, in 4 states.